HAL-Université de Bretagne Occidentale
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Discovering Data Manifold Geometry via Non-Contracting Flows
No full textWe introduce an unsupervised approach for constructing a global reference system by learning, in the ambient space, vector fields that span the tangent spaces of an unknown data manifold. In contrast to isometric objectives, which implicitly assume manifold flatness, our method learns tangent vector fields whose flows transport all samples to a common, learnable reference point. The resulting arc-lengths along these flows define interpretable intrinsic coordinates tied to a shared global frame. To prevent degenerate collapse, we enforce a non-shrinking constraint and derive a scalable, integration-free objective inspired by flow matching. Within our theoretical framework, we prove that minimizing the proposed objective recovers a global coordinate chart when one exists. Empirically, we obtain correct tangent alignment and coherent global coordinate structure on synthetic manifolds. We also demonstrate the scalability of our method on CIFAR-10, where the learned coordinates achieve competitive downstream classification performance
Atmosphere, Ocean and coupled Ocean-Atmosphere Models in a single code
No full textInternational audienceA new coupled ocean–atmosphere model is presented. It permits the study of turbulent interactions between the atmosphere and the ocean at very fine scales within a single coherent model code (the Meso–NH model).First, an ocean model is developed from the Meso–NH atmospheric model with only a few modifications. By exploiting the isomorphism between the equations governing the two fluids, the same hydrodynamical algorithm is used to simulate both the atmosphere and the ocean. The main difference in the numerical code is related to the distinct state equations describing the ocean and the atmosphere. The ocean model is then applied to idealised cases of shallow and deep convection, as well as to a diurnal warm-layer case observed during CINDY–DYNAMO.Because atmospheric and oceanic models share a single code base, they automatically share many key features such as numerical schemes and subgrid turbulent representations. The coupling between the ocean and atmosphere is therefore straightforward, internally consistent, and does not require an external coupler. The ocean model as well as the coupled one directly benefits from all existing and future developments of the atmospheric model, such as grid nesting, turbulence statistics, budget diagnostics, maintenance, and ongoing computational improvements.Finally, a first test of the coupled model at fine scales (LES) is presented
Ochratoxin A and citrinin production and migration in Penicillium verrucosum molded strawberry jams
No full textInternational audienceFood losses and waste have become a major worldwide challenge, partly due to mold spoilage at the consumer level. One possible way to reduce food waste due to moldy foods would be to avoid a too conservative approach where products are directly discarded if fungal growth is observed. However, a food safety risk exists as many fungal species produce potentially toxic mycotoxins that can migrate into foods, so this hazard needs to be considered to establish consumer recommendations. This study quantified citrinin and ochratoxin A accumulation and migration in strawberry jams after inoculation with Penicillium verrucosum UBOCC 109221 and incubation at 8 and 20 • C. The mold failed to grow after 28days of incubation at 20 • C on jam with 59% sugar content but exhibited a constant growth rate of about 1.15 mm/d on the other sugar concentrations. After 14 days of incubation, citrinin concentration (10000 ng/g) for the jam containing 34 % sugar was about twice the concentration observed for 39 and 44 % sugar. Mycotoxin migration experiments were then carried out for 39 % sugar content and showed that the maximum mycotoxin concentrations were obtained for the 5 cm lesion diameter. At 20 • C, citrinin concentration (30 000 ng/g) was about twice that obtained at 8 • C, while the maximum ochratoxin A concentration was about 100 ng/g. For 1 and 2 cm lesions with 8 • C storage, mycotoxins were not detected at 3 cm depth, accordingly jam can be consumed after removing about 2 to 3 cm beyond the moldy area. For greater lesions, jam should be discarded because mycotoxins were detected at >4 cm depth
Vibration and stability of two-phase peridynamic Euler-Bernoulli beams under general boundary conditions - Exact and numerical approaches
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Assessing health risks associated with energy poverty in French households using structural equation modelling.
No full textInternational audienceEnergy poverty, acknowledged for its significant impact on health, has become a policy priority in most European countries. Despite increasing attention, the social and health mechanisms through which energy poverty affects well-being remain insufficiently explored. This study uses data from a national survey conducted in mainland France in 2019 (N = 1000 households), to explore the effects of energy poverty on mental and physical health. We construct a multidimensional energy poverty index based on housing satisfaction, mildew/dampness, heating deprivation, and thermal discomfort, and adapt the Short Form health scale. Using structural equation modelling, we show that energy poverty is associated with poorer physical and mental health with physical health partially mediating its effect. Socio-demographic factors including age, gender, housing status, tobacco use, and energy expenditures further amplify these associations. Policy recommendations address the multidimensional nature of energy poverty and its health impacts, providing insights relevant to other countries facing similar challenge
The North Balearic Front as an ecological boundary: zooplankton fine-scale distribution patterns in late spring
No full textInternational audienceObservations, models and theory have suggested that ocean fronts are ecological hotspots, generally associated with higher diversity and biomass across many trophic levels. Nutrient injections are often associated with higher chlorophyll concentrations at fronts, but the response of the zooplankton community is still insufficiently understood. The present study investigates mesozooplankton stocks and composition during late spring, northeast of Menorca, along two north-south transects that crossed the North Balearic Front separating central waters of the Northwestern Mediterranean Sea gyre from peripheral waters originating from the Algerian basin. During the BioSWOT-Med campaign, vertical triple-net tows with 200 and 500 µm meshes were carried out at three depths (100, 200, and 400 m), and the samples were processed with ZooScan to classify organisms into eight taxonomic groups. Zooplankton distributions were analyzed for the surface layer (0–100 m), a mid-depth layer (100–200 m), and a deeper layer (200–400 m). The results did not show a significant increase in biomass in the front in any layers. The NBF appears to act as a boundary between communities rather than a pronounced area of active or passive zooplankton accumulation. Analyses of stratified vertical distributions of zooplankton highlighted distinct taxonomic compositions in the three layers, and a progressive homogenization of community structure with depth, reflecting a weaker impact of hydrological processes on deeper communities. The clearest impact of the front was within the upper 100 m, where the mesozooplanktonic taxonomic composition differed between the front and adjacent water masses, with a decrease in all taxonomic groups except Cnidaria, which increased dramatically. In the two deeper layers, the front also influenced community composition, although to a lesser extent, with marked increases in Foraminifera and Cnidaria. Moreover, the northern water mass and the front were dominated by large copepods, while the southern water mass exhibited higher zooplankton diversity and smaller-sized copepods. The results of this study highlight the complexity of processes shaping planktonic communities over time and space in the NBF zone and its adjacent waters. These processes include zooplankton stock reduction in the transitional post-bloom period, marked effect of diel variation linked to vertical migrations, and potentially the impact of storm-related mixing in the surface layer that can disrupt established ecological patterns
The immune cell landscape analyzed by imaging mass cytometry in the muscle of patients with inclusion body myositis associated or not with Sjögren’s disease
No full textInternational audienceAbstract Objectives Several studies reported an association between Sjögren’s disease (SjD) and inclusion body myositis (IBM). However, the potential specificities of IBM when associated with SjD have been poorly investigated. Here, we compared the muscular inflammatory infiltrates between IBM patients with or without associated SjD. Materials and methods Formalin-fixed and paraffin-embedded muscle biopsies of patients with IBM, associated with SjD (IBM-SjD) and sporadic (sIBM) forms, from 6 French expert centers, were collected. Imaging mass cytometry (IMC) multiplex immunostaining (34 markers) was used to quantify and analyze inflammatory infiltrate composition. Supervised and unsupervised descriptive and comparative analyses were performed. Results Fourteen IBM-SjD and 7 sIBM muscle samples were analyzed. No statistically significant difference was encountered but some trends were pointed. IBM-SjD samples had a broader inflammatory infiltrate surface (median 4.8%, IQR: 1.4–8.6) than sIBM samples (median 1.6% IQR: 1.2–2.4). In both groups, the main inflammatory cells in muscle infiltrate were primarily macrophages and T cells. However, the proportion of plasma cells (14.7% IQR: 5.4–24.6 vs 8.5% IQR: 4.6–9.8) and B cells (3.1% IQR: 0.4–5.6 vs 0.5% IQR: 0.0–3.2) were higher in IBM-SjD patients. Conclusion Using IMC on muscle biopsies, IBM-SjD and sIBM patients share common histological features, but there are notable distinctions (more extensive infiltrate, high numbers of B cells and plasma cells in IBM-SjD). These observations were exploratory and based on a small number of patients. but may suggest IBM-SjD has distinct SjD-related pathophysiology compared with sIBM, and open to further research with potential diagnostic and therapeutic implications
